The present invention relates generally to lawn maintenance equipment and relates more particularly to an apparatus for aerating turf by sequentially driving sets of coring tines into the ground to remove substantially cylindrical turf cores with a minimal disturbance of the surrounding turf area.
The importance of aerating lawns to permit water, oxygen and nutrients to reach the grass root region has been recognized for some time by experts in lawn care, particularly those involved in maintaining functional lawn areas such as golf courses, athletic fields, etc. A variety of types of equipment have been devised for aerating turf, some of which simply cut slits in the earth, while others either displace or remove small turf portions at spaced intervals.
Turf aerating equipment can basically be divided into two broad types, the simplest of which is the rotary type which typically involves a roller or rotatably mounted elements equipped with soil penetrating elements, which usually comprise disc-like knives, spoon tines or hollow coring tines. Although the knife-equipped roller type aerator provides a fairly clean slicing action of the turf, a rotary type device using fixed spoon tines or coring tines tends to disturb and tear up the area immediately surrounding the tine holes and thus is not suitable for critical lawn surfaces such as golf course greens.
A second and more complex type of aerating equipment is the reciprocating type which employs hollow coring tines which are driven substantially vertically into the ground in a reciprocating fashion. Such devices not only cause less damage to the surrounding lawn surface, but in addition are usually capable of achieving a deeper penetration of the soil than rotary type aerators. The present invention is directed to such a reciprocating type aerating device.
Since it would be impractical to stop the forward motion of the machine each time a set of tines was driven into the ground, reciprocating aerators must include a mechanism for accommodating the necessary relative horizontal movement of the tines and the aerator frame during turf penetration and for repositioning the tines preparatory to their next downward stroke. The aerator mechanism should, in addition, maintain a substantially vertical disposition of the tines during their contact with the ground.
In prior devices, these functions have been accomplished in several different ways. In an early form of aerating device, the vertically reciprocated tine arms were connected with a simple crank movement at their upper ends and spring loaded toward a stop plate at their lower ends such that engagement with the ground would extend the tension springs as the machine moved away from the ground engaging tines. Upon emergence of the tines from the ground, the springs would return the tine arms to a position against the stop ready for the next ground engagement. Although such a device provided the requisite relative movement between the tines and the machine frame, the arcuate movement of the tines while engaged with the ground resulting from the forward travel of the upper pivoted ends of the tine arms resulted in a substantial disturbance of the ground in the vicinity of the core holes. In addition, the sliding of the tine arms along guides and the impacting of the arms against the stop resulted in considerable friction, wear and a noisy operation of the device.
In an effort to overcome the shortcomings of the early reciprocating type aerators, later devices employed mechanisms for positively controlling the lower ends of the tine arms, such mechanisms being interconnected with the forward drive mechanisms of the machine to prevent tearing of the turf by the engaged tines.
In one popular device of this type, the vertically reciprocating tine arms are carried by slides which are oscillated horizontally by a rotating cam. While the cam and slide arrangement provides a reasonably good tine motion, the mechanism is complex, expensive to manufacture and maintain, and requires a significant amount of power to drive the slides, tine arms and tines in translational movement.